JP2023170732A - Photocurable resin composition - Google Patents

Abstract

To provide a photocurable pressure-sensitive resin composition that can be used in laminate sheets represented by an information-carrying sheet, and can maintain consistent re-peelability after being bonded through photocuring without experiencing a rapid increase in peeling force over time.SOLUTION: A photocurable re-peelable pressure-sensitive resin composition includes an ethylene oxide-modified bisphenol A diacrylate, an acrylic block copolymer, a hydroxy group-containing (meth)acrylate, and a photopolymerization initiator. An ethylene oxide (EO) modification level in the ethylene oxide-modified bisphenol A diacrylate is 5-20. The ethylene oxide-modified bisphenol A diacrylate constitutes 36-46 wt.% of the total solid content.SELECTED DRAWING: None

Description

The present invention relates to a pressure bonding resin composition that is cured by light such as ultraviolet rays and has good removability.

Traditionally, sealed letters have been used to send information while keeping it hidden, but now information can be written on the inside of a V-shaped or Z-shaped postcard and then glued together, making it possible to mail it while keeping it hidden. Postcards have come into use and are generally collectively referred to as information carrying sheets.

The adhesive used for this information-carrying sheet must have the characteristics of being easy to peel but difficult to re-adhere, and initially water-based latex or emulsion was used, and in the past the applicant also used vinyl acetate emulsion. has invented a composition consisting of a plasticizer and fatty acid calcium (Patent Document 1). However, these water-based adhesives have many problems, such as requiring a long time to dry after application, and the paper that serves as the base material tends to expand, contract, and warp due to moisture absorption.

Therefore, UV-curable adhesives that can be cured in a short time have come to be used as adhesives that can address these problems. He has invented a composition consisting of di(meth)acrylate, a nonfunctional acrylic polymer, and a photopolymerization initiator (Patent Document 2). This composition had excellent properties in that it did not easily warp even if it was applied to a substrate and left to stand after curing, and it was unlikely to cause defects during the bonding process. However, if it is left for a long time after bonding, the peeling force may increase to the point where it becomes difficult to re-peel it. Photocuring allows stable re-peelability to be maintained without a sudden increase in peeling force over time. A strong adhesive was needed.

Patent No. 5008934 JP2021-075614

The object of the present invention is to maintain stable removability without a sudden increase in peeling force over time, which can be used for laminated sheets such as information-carrying sheets, and after being cured with light and bonded together. The purpose of the present invention is to provide a pressure-bonding resin composition that can be used.

In order to achieve the above-mentioned object, the invention of claim 1 comprises: ethylene oxide-modified bisphenol A diacrylate (A); an acrylic block copolymer (B); a hydroxyl group-containing (meth)acrylate (C); agent (D), the EO modification amount of (A) is 5 to 20, and the amount of (A) blended is 36 to 46% by weight based on the total solid content. A mold removable pressure bonding resin composition is provided.

The invention according to claim 2 provides the photocurable removable pressure bonding resin composition according to claim 1, wherein the (B) is a triblock copolymer elastomer of methyl methacrylate and butyl acrylate. .

The invention according to claim 3 provides the photocurable removable pressure-bonding resin composition according to claim 1 or 2, further comprising a reactive diluent (E).

A fourth aspect of the present invention provides a pressure bonding paper having a cured layer of the photocurable removable pressure bonding resin composition according to any one of the first and second aspects.

The composition of the present invention can maintain stable removability without a sudden increase in peeling force over time, even after being applied to a substrate, cured with light, and bonded together. It is useful as a resin composition for.

The composition of the resin composition of the present invention is ethylene oxide-modified bisphenol A diacrylate (A), an acrylic block copolymer (B), a hydroxyl group-containing (meth)acrylate (C), and a photopolymerization initiator (D). ). Note that in this specification, (meth)acrylate includes both acrylate and methacrylate.

The ethylene oxide (hereinafter referred to as EO)-modified bisphenol A diacrylate (A) used in the present invention is a compound represented by the following general formula (1), and has improved curability and an increase in peeling force over time. Blended for the purpose of suppressing excessive hardening progress.

...(1)
(n and m are each independently 1 or more, and n+m is an integer from 5 to 20.)

(A) has a low viscosity because it has been modified with EO, and the acryloyl groups, which are reactive functional groups, can maintain a certain distance from each other, so the crosslinking density does not become excessively high, and internal stress remaining in the coating film and hardening are reduced. Shrinkage can be reduced. Therefore, it is possible to achieve a good balance between the adhesion of the substrate and the strength of the coating film, and it is possible to form a cured film that is also flexible. The total number of EO modifications added per molecule is 5 to 20, preferably 8 to 12, and particularly preferably 10. If the number of EO modifications is less than 5, the peeling force may decrease, and if the number of EO modifications is more than 20, the peeling force over time may become too strong.

The blending amount of (A) based on the total solid content is 36 to 46% by weight, preferably 37 to 45% by weight, and particularly preferably 38 to 44% by weight. If it is less than 36% by weight, sufficient initial peeling force may not be ensured, and if it exceeds 46% by weight, it may not be possible to sufficiently suppress an increase in peeling force over time or excessive progress of curing.

The acrylic block copolymer (B) used in the present invention is a plasticizer-like component that does not participate in the curing reaction, reduces warpage by stress relaxation, and provides appropriate initial peeling force and peeling without adhesive residue. Take on the role of making it possible. "Acrylic" includes at least one structural unit derived from a monomer selected from the group consisting of (meth)acrylic acid, fumaric acid, maleic acid and its esters, and (meth)acrylamide and its derivatives. Among these, copolymers of (meth)acrylic acid and its esters are preferred.

Examples of the structure of (B) include linear block copolymers, branched (star-shaped) block copolymers, etc., but linear block copolymers are preferred from the viewpoint of cost. Regarding linear block copolymers, diblock copolymers (A-B) composed of two types of monomers (A and B) and Triblock copolymer (ABA) is more preferred

As the monomer constituting the above-mentioned (B), methyl methacrylate (hereinafter referred to as MMA) is preferable because the cured resin has good strength and transparency and is easily and inexpensively available. Further, n-butyl acrylate (hereinafter referred to as BA) is preferred because the cured resin has excellent flexibility and can exhibit good adhesive properties. A block copolymer composed of MMA and BA is, for example, a block copolymer composed of a hard segment composed of P (poly) MMA and a soft segment composed of P (poly) BA, with both ends of the soft segment sandwiched between the hard segments. A block structure (PMMA-PBA-PMMA), etc. may be mentioned. This structure has the characteristics of having both the transparency and weather resistance of PMMA and the flexibility and adhesiveness of PBA.

When the above (B) is a PMMA-PBA-PMMA triblock copolymer, the copolymerization ratio of MMA is preferably 10 to 50% by weight so that the balance between adhesive strength and removability is appropriate. , 15 to 45% is more preferable. By setting the copolymerization ratio of MMA to 10% or more, the adhesive strength is moderate and it is difficult to leave adhesive residue when peeled off, ensuring sufficient removability, and by setting it to 50% or less, the hardness is sufficient without becoming too high. Ensures good adhesion.

When the above (B) is a PMMA-PBA-PMMA triblock copolymer, two or more types of copolymers having different MMA ratios may be used in combination. In that case, the MMA ratio is used as a guideline for the blending ratio as in the case of using it alone, and the sum of the MMA ratio of each different copolymer multiplied by its content ratio is 10 to 50% by weight. (For example, if the blending amount with an MMA ratio of 50% by weight is 40% and the blending amount with an MMA ratio of 30% by weight is 60%, 50% by weight x 0.4 + 30% by weight x 0.6 = 38 weight %).

The weight molecular weight (hereinafter referred to as Mw) of the above (B) is preferably 30,000 to 200,000, more preferably 50,000 to 150,000, and a sufficient initial peeling force is ensured by setting it to 30,000 or more. By setting the molecular weight to 200,000 or less, sufficient solubility in the monomer component and a viscosity suitable for workability can be ensured. Note that Mw was calculated by measuring the molecular weight in terms of standard polystyrene by gel permeation chromatography using a column using a styrene divinylbenzene-based packing material and using a tetrahydrofuran eluent.

The blending amount of (B) based on the total solid content is preferably 1.0 to 20% by weight, more preferably 2.0 to 15% by weight, and particularly preferably 3.0 to 10% by weight. By setting the content to 1.0% by weight or more, sufficient initial peeling force can be ensured, and by setting the content to 20% by weight or less, sufficient solubility can be ensured, and the viscosity can be easily adjusted to be suitable for coating. .

The hydroxyl group-containing (meth)acrylate (C) used in the present invention is blended for the purpose of dissolving component (B) and improving the curability of the composition. There is no particular limitation as long as it contains a hydroxyl group, but from the viewpoint of curing shrinkage, it is preferably bifunctional or less, and more preferably monofunctional. For example, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 1,4- Examples include cyclohexanedimethanol monoacrylate and 4-hydroxycyclohexyl (meth)acrylate, which can be used alone or in combination of two or more. Among these, 4-hydroxybutyl acrylate (hereinafter referred to as 4HBA) is preferred because (B) has very good solubility.

The blending amount of (C) based on the total solid content is preferably 5 to 25% by weight, more preferably 8 to 20% by weight, and particularly preferably 10 to 18% by weight. By setting the content to 5% by weight or more, sufficient solubility of (B) can be ensured, and by setting the content to 25% by weight or less, sufficient initial peeling force can be ensured.

The photopolymerization initiator (D) used in the present invention is a benzyl ketal, acetophenone, or phosphine oxide type that generates radicals when irradiated with ultraviolet rays or electron beams, and these radicals trigger a polymerization reaction. General-purpose photopolymerization initiators can be used. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, curability can be imparted over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, 2,2-dimethoxy-1,2-diphenylethan-1-one is used as a benzyl ketal type, and 1-hydroxy-cyclohexyl-phenyl-ketone and 1-[4-(2- hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one is converted into 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1 as an α-aminoacetophenone system. -one is acylphosphine oxide, such as 2.4.6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2.4.6-trimethylbenzoyl)-phenylphosphine oxide, either singly or in combination. Can be used in combination.

Among the above (D), it is preferable to include α-hydroxyacetophenone, which is resistant to yellowing. Commercially available products include Omnirad 184 and Omnirad 2959 (trade name: manufactured by iGM).

The amount of (D) to be blended is preferably 5 to 15 parts by weight, more preferably 8 to 12 parts by weight, per 100 parts by weight of the photopolymerizable component. By blending within this range, the composition can be efficiently cured without being added excessively.

It is preferable that the composition of the present invention further contains a reactive diluent (E). By blending (E), the viscosity can be adjusted to suit workability. (E) is preferably a di- to tetrafunctional (meth)acrylate, more preferably a trifunctional (meth)acrylate, depending on the balance between reactivity and curing shrinkage, and is compatible with (A), (B), and (C). Particularly preferred are (meth)acrylates (excluding (A)) having an ether skeleton such as those modified with alkylene oxide because of their good properties.

Examples of (E) include EO-modified glycerin tri(meth)acrylate, propylene oxide (hereinafter referred to as PO)-modified glycerin tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, and PO-modified trimethylolpropane tri(meth)acrylate. Examples include meth)acrylates, which can be used alone or in combination of two or more types. Among these, tri(meth)acrylate derived from glycerin is preferred because it has high reactivity and is less prone to warping, and PO-modified glycerin triacrylate is more preferred from the viewpoint of availability. The blending amount of (E) is preferably 40% by weight or less, more preferably 35% by weight or less.

The composition of the present invention may contain leveling agents, tackifiers, antioxidant pigments, dyes, light stabilizers, antifoaming agents, ultraviolet absorbers, wettability regulators, etc. as necessary to the extent that performance is not impaired. Various additives may be included.

Leveling agents include polydimethylsiloxane, polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, etc., and they can be used alone or in combination of two or more. Among these, polyester-modified polydimethylsiloxane is preferred because of its excellent compatibility with (A).

The viscosity of the present composition at 25° C. is preferably 50 to 1,000 mPa·s, more preferably 100 to 800 mPa·s. By setting it to 50 mPa·s or more, it becomes easy to ensure a sufficient coating amount, and by setting it to 1,000 mPa·s or less, sufficient coating smoothness can be ensured.

It is preferable that the peel strength (initial peel strength) immediately after applying and curing the present composition to a base material and pressing it is 6 N/6 inch or more, and that there is no breakage of the base material. Further, it is preferable that the peel strength after curing at 23° C. for 7 days after bonding (time-lapse peel strength) is 30 N/6 inch or less, and there is no breakage of the base material. If the strength is within this range, it can be said that sufficient removability is ensured for practical use.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but these are intended to be specific examples and are not particularly limited to these. Unless otherwise specified, the measurements were performed at a room temperature of 25° C. and a relative humidity of 65%. Further, the blending amount indicates parts by weight.

Examples 1 to 6
In a light-shielding bottle, Miramer M2100 (trade name: manufactured by Miwon Co., Ltd., EO modification number 10) was placed as (A), and KURARITY LA2140 (trade name: manufactured by Kuraray Co., Ltd., PMMA-PnBA-PMMA triblock copolymer) was placed as (B). , Mw77,000, MMA ratio 20%) and KURARITY LA2330 (trade name: manufactured by Kuraray Co., Ltd., the same triblock copolymer, Mw122,000, MMA ratio 20%) and KURARITY LA2270 (trade name: manufactured by Kuraray Co., Ltd., the same triblock copolymer, Mw122,000, MMA ratio 20%) block copolymer, Mw 70,000, MMA ratio 40%), 4-HBA (trade name: 4-hydroxybutyl acrylate, manufactured by Osaka Organic Chemical Co., Ltd.) as (C), Omnirad 184 (manufactured by iGM, Ltd.) as (D), Add M-320 (product name: Miwon, PO modified glycerin triacrylate, PO modified number 3) as (E) in the amount shown in Table 1, and use a stirring deaerator to homogenize the mixture. The resin compositions of Examples 1 to 6 were prepared by stirring until the mixture was mixed.

Comparative examples 1 to 6
In addition to the materials used in the examples, a light-shielding bottle was filled with Miramer M-2300 (product name: manufactured by Miwon, EO modification number 30) and Miramer M240 (product name) as bisphenol A diacrylates with different EO modification numbers from (A). : manufactured by Miwon Co., Ltd., EO modification number 4) was added in the amount shown in Table 2, and stirred using a stirring deaerator until uniformity was obtained to prepare resin compositions of Comparative Examples 1 to 6.

Preparation of evaluation sheet The resin composition was applied to New V Mat (product name: Mitsubishi Paper Mills Co., Ltd., matte coated paper) using Bar Coater #8, and the resin composition was irradiated with electrode UV irradiation made by Eye Graphic Co., Ltd. Using the equipment Eye Mini Grandage ECS-151U, cure with a high-pressure mercury lamp under the conditions of output 90 mW/cm ² and cumulative light intensity 80 mJ/cm ² , fold in half with the coated side facing inside, and overlap the cured resin surfaces. An evaluation sheet was prepared by crimping using a postcard crimping machine PRESSLE Bee manufactured by Toppan Forms.

The evaluation method was as follows.

Viscosity: Using a cone plate type viscometer RC-550 manufactured by Toki Sangyo, 25 ± 1 ° C with a cone angle of 3°R17.65, rotation speed is 100 rpm for viscosity range of 500 mPa・s or less, 30 rpm for 500 to 2000 mPa・s 50 to 1,000 mPa·s is marked as ○, and cases outside this range are marked as ×.

Peeling force: The laminated sheet was cut to 150 mm x 6 inches, and T-shaped peeling was performed at a peeling speed of 300 mm/min using a tensile tester TGI-1kN manufactured by Techno Graph. The initial peeling force was immediately after the pressure bonding, and the peeling force after curing for 7 days at 23° C. was the temporal peeling force. In the initial peeling force, 6 N or more was rated as ○, and less than 6 N was rated as ×. In addition, in terms of peeling force over time, 6 to 30 N was rated as 0, and cases outside this range were rated as ×.

Broken base material: The condition of the base material after the peel test was visually confirmed, and the case where there was no material breakage was rated ○, and the case where there was material breakage was rated ×.

Evaluation results The evaluation results are shown in Tables 3 and 4.

The resin compositions of Examples were evaluated favorably in terms of viscosity, initial peeling force, peeling force over time, and substrate breakage.

On the other hand, Comparative Example 1 in which (A) is below the lower limit has a small initial peeling force, Comparative Example 2 in which (A) is above the upper limit has a large peeling force over time, and Comparative Example 6 in which (A) is not blended has an initial peeling force. was small, and the peeling force over time was too strong. Furthermore, Comparative Example 3 in which (C) was not blended did not dissolve, Comparative Example 4 with a large number of EOs had too strong peeling force, and Comparative Example 5 with a small number of EOs had a small peeling force, all of which were not suitable for the present invention. Met.

Claims (4)

The above-mentioned (A) contains ethylene oxide-modified bisphenol A diacrylate (A), an acrylic block copolymer (B), a hydroxyl group-containing (meth)acrylate (C), and a photopolymerization initiator (D). A photocurable removable pressure bonding resin composition, characterized in that the amount of EO modification is 5 to 20, and the amount of (A) blended is 36 to 46% by weight based on the total solid content. 2. The photocurable removable pressure bonding resin composition according to claim 1, wherein said (B) is a triblock copolymer elastomer of methyl methacrylate and butyl acrylate. The photocurable removable pressure-bonding resin composition according to claim 1 or 2, further comprising a reactive diluent (E). A pressure bonding paper having a cured layer of the photocurable removable pressure bonding resin composition according to claim 1 or 2.